Admittedly I have not seen a lot of either Gray or Kwame. What I know about Gray I remember from his days at Pitt. I always thought he'd be a servicable backup C for a contending team - coming from Pitt you know a) they win, and b) they play hard.
Kwame will always be remembered as a bust, but hey, we took a shot on Kandi-man didn't we?
My guess is that whoever is a better fit defensively would have the upper hand.